Apparatus for making pictorial parallax panoramagram units

ABSTRACT

Apparatus for making pictorial parallax panoramagram units wherein a coating roll, a pressure roll and a forming roll are mounted in parallel relationship to form a pair of spaced-apart nips, the first such nip being formed between the coating roll and the pressure roll and the second such nip being formed between the pressure roll and the forming roll. The coating roll is heated and a metering means cooperates therewith to form a predetermined thickness of plastic material which is fed to the first nip. A backing sheet is fed by suitable means through the first and second nips, and at the first nip, the metered layer of plastic is applied to the backing sheet. The forming roll is chilled so that as the backing sheet with the plastic thereon passes through the second nip, the plastic material is set to conform to the configuration of the surface of the forming roll.

United States Patent Rice et a1.

APPARATUS FOR MAKING PICTORIAL PARALLAX PANORAMAGRAM UNITS Harold D.Rice, Leawood, Kans.; Sam L. Leach, St. Louis, Mo.

Assignee: Pid Corporation, Beverly Hills, Calif.

Filed: Jan. 6, 1965 App]. No.: 436,976

Related U.S. Application Data Division of Ser. No. 202,930, May 14,1962, Pat. No. 3,241,429.

lnventors:

U.S. Cl. ..l56/500, 118/415, 156/356, 156/553, 156/582 Int. Cl ..B29bB32b 31/00 Field of Search ..161/88, 33, 3; 156/209, 280, 156/519, 553,363, 364, 366, 367, 356, 500, 553,

References Cited UNITED STATES PATENTS Leach....-..... ..117/10 Rullo 156/472 X 2,714,571 8/1955 lrion et a1 .156/311 X 2,758,045 8/1956 Heatonet a1 161/88 X 2,759,866 8/1956 Seymour 161/254 X 2,992,152 7/1961Chapman 156/280 X 3,024,154 3/1962 Singleton et a1. ..l56/209 3,071,180l/1963 Finger et a1 ..156/5l9 Primary Examiner.lohn T. GoolkasianAssistant Examinerl-lenry F. Epstein Attorney-Holman & Stern [57]ABSTRACT Apparatus for making pictorial parallax panoramagram unitswherein a coating roll, a pressure roll and a forming roll are mountedin parallel relationship to form a pair of spaced-apart nips, the firstsuch nip being formed between the coating roll and the pressure roll andthe second such nip being formed between the pressure roll and theforming roll. The coating roll is heated and a metering means cooperatestherewith to form a predetermined thickness of plastic material which isfed to the first nip. A backing sheet is fed by suitable means throughthe first and second nips, and at the first nip, the metered layer ofplastic is applied to the backing sheet. The forming roll is chilled sothat as the backing sheet with the plastic thereon passes through thesecond nip, the plastic material is set to conform to the configurationof the surface of the forming roll.

3 Claims. 'Jrawing Figures iMENTEUJANY B1972 SHEET 1 [1F 2 PATENIEDJmawiz SHEET 2 OF 2 5eo\ 540 F g 3 554 562 46 Fig: 5

500 506 4? INVENTORS HAROLD D. RICE SAM L. LEACH APPARATUS FOR MAKINGPICTORIAL PARALLAX PANORAMAGRAM UNITS This application is a division ofour copending application, Ser. No. 202,930, filed May 14, 1962, and isentitled to the priority date thereof.

This invention relates broadly to optical display units, and isparticularly concerned with the provision of optical display unitsincorporating lenticular screens. Such display units are genericallyknown in the art as pictorial parallax panorama gram units.

SPECIFIC METHOD OBJECTS To provide practical and commercial methods ofproducing the products according to the preferred embodiments, a methodis used which provides for applying a coating directly to animage-carrying layer, and then embossing the coating to form the sameinto a lenticulated optical screen. The coating is applied as a fluidflowable viscous material which is subsequently set to afford permanencyin formation, and flexibility in use without affecting thecharacteristics of the image-carrying layer. The coating is free of anyplasticizer so as to eliminate allergy or bleeding problems or the likewhen applied to the base layer. The method includes steps affordingapplication of the coating in a controlled thickness to ensureuniformity in the ultimate screen, and the utilization of a minimum ofmaterial. The plastic material is applied in time sequence to themovement of the image-carrying base.

It is to be understood that the invention of this application lies inthe provision of apparatus'adapted to carry out such method so as'toproduce the desired products. Thus, with respect to the preferredembodiment of the apparatus, specific objects of the invention includethe following: (a) the provision of an automatic apparatus adapted toperform the method steps of the preferred embodiment hereof outlinedhereinabove; (b) the provision of such an apparatus which includes meansfor automatically timing a sequential processing operation in accordancewith the method of the preferred embodiment hereof; (c) the provision ofsuch an apparatus which is applicable to the formation of lenticularscreen pictorial parallax panoramagram units, as well as to generalcoating techniques; (d) the provision of such an apparatus wherein thebase layer being coated is passed about rollers for purposes of havingthe coating applied thereto; (e) the provision of such an apparatuswhich incorporates a grooved embossing roller for purposes of formingthe applied coating into a lenticular screen; (f) the provision of suchan apparatus which includes a reservoir for holding and heating plasticto be applied to the base layer, and means for opening and closing thereservoir in timed relation to the movement of a base layer travelingthereunder; (g) the provision of such a basic apparatus which pennitsadjustment in the thickness of the coating being applied; (h) theprovision of such an apparatus which includes means cooperating with theroller means thereof to ensure uniformity in coating, as well asuniformity in formation of the coating into a lenticular screen; (i) theprovision of such an apparatus which can be operated over extendedperiods of time for commercial production, and without shutdown.

In accordance with the basic aspects hereof, a pictorial parallaxpanoramagram unit comprises a flexible optical display. The displayincludes a lenticulated image layer and a lenticular screen having abase face and a lenticulated forward face. The image layer is fixed indirect contact with the base face of the screen, and in alignment withthe lenticles defined by the forward face thereof. Preferably, the focalpoint of the lenticles of the screen lie at least substantially in theplane of the image layer, i.e., at a point which affords the bestoptical clarity with a planar rear face adjacent the image layer. Thescreen has a maximum thickness of between 0.005 and 0.025 inches.

In accordance with the preferred embodiment hereof, the unit ismanufactured by applying a flowable coating of the plastic, preferably apolymer of an ethelinically unsaturated hydrocarbon, in a viscous stateonto a Iineated image layer preferably in sheet form, and thereafterembossing the coating into the form of lenticles properly aligned withthe lineations on the image layer. The plastic is preferably such thatit has a melt temperature of between 275 and 350 F., and a coatingviscosity of between I0 and 200 poises. Moreover, the chill temperatureof such plastic is such that it permits the application of the plasticand subsequent forming thereof, while at the same time allowing forsetting as the plastic is engaged by a forming embossing-type roller.Preferably, the embossing roller is chilled to properly set the plastic,but after setting the plastic, maintains its flexible characteristics,and affords a screen having a flexibility of between 0.] and 2.0 I0p.s.i.

The apparatus for producing a unit in accordance with the aforesaidpreferred embodiment includes a series of rollers adapted to carry outthe method steps, as well as a controllable reservoir for depositing theplastic on the image layer as the image layer passes thereunder.Preferably, the apparatus also includes sequentially operated grippingmeans and a vacuum type pickup feed. Additionally, the preferred form ofapparatus includes gear-operated timing means to insure propersequential operation.

The above basic aspects of the preferred embodiment hereof and preferredmodification hereof, as well as other important features of theinvention, will be better comprehended, and the invention as a wholewill be better understood, when consideration is given to the followingdetailed description thereof. Such description refers to the annexeddrawings, presenting preferred and illustrative embodiments of theinvention. In the drawings:

FIG. 1 is a fragmental enlarged perspective view of a pictorial parallaxpanoramagram unit constructed in accordance with the preferredembodiment hereof;

FIG. 2 is a side schematic view of a preferred processing assemblyutilized to produce the type of products with which the invention isprimarily concerned;

FIG. 3 is a schematic side view presenting structural aspects of thedevices hereof to be used with the assembly of FIG. 2;

FIG. 4 is a perspective view of a preferred form of plastic dischargecoating means incorporated in the system of FIG. 3; and a FIG. 5 is atransverse sectional view of the coating means shown in FIG. 4.

If reference is not made to FIG. 1, it will be seen that such FIGUREpresents a pictorial parallax panoramagram unit or optical displaygenerally designated by the numeral 2. Such unit or display comprises alineated image layer 4 and a lenticular screen 6 fixed directlythereover. The lenticular screen 6 has a base face 8 and a lenticulatedforward face 10. The image layer 4 is fixed in direct contact with thebase face 8 of the screen 6, free of any adhesive interposed between thescreen 6 and image layer 4. The lenticular screen 6, or moreparticularly, the lenticulated face 10 thereof, comprises a series ofsemicylindrical or partially cylindrical curves forming the forward faceof elongated lens elements generally designated by numeral 12. Each ofthe lens elements, as shown, comprises a simple lens of the type havinga circularly curved, forward face, and a planar rear face. The focalpoint of the lenticles 12 of the screen lies at least substantially inthe plane of the base thereof, or in the plane of the image carried bythe image layer 4.

The image layer is applied to a base sheet 30 (FIG. 2) and thelenticular screen is formed thereover in accordance with the preferredembodiments hereof. As shown in FIG. 2, a pair of feed rollers 40 aresuitably positioned to feed the base sheet to and past the stationswhere subsequent operations will be performed. The first operation isthat of depositing. on the base sheet 30 a coating. For this purpose,disposed at the first operation station is an extruder 42 which feeds adepositing trough 44 having a movable wall 46. Disposed directly underand in vertical alignment with the outlet 48 of the trough 44 is acoating cylinder 50. This coating cylinder merely comprises a rollerhaving a smooth surface, and carrying means for gripping thereon thebase sheet 30. Disposed laterally, and supported for rotation on an axisdisposed vertically above, the coating cylinder, is an ironing cylinder52. This ironing cylinder preferably has a smooth chrome-plated circularsurface 54. The ironing cylinder 52 is so positioned that it forms withthe coating cylinder 50 a nib passageway 56.

According to the invention, the sheet 30 is fed between the feed rollers40 and under the depositing trough 44. As the sheet passes under thedepositing trough 44, a plastic coating 60 is deposited thereon. Forthis purpose, the movable side 46 of the trough 44 is raised to open theoutlet 48, and allow the plastic material to flow under gravitationalaction from the trough and onto the surface of the sheet 30. The printedtop surface 34 of sheet 30 faces the trough so that such surface whichcarries the image has the plastic composition thereon. The trough 44,quite naturally, is provided with suitable means to raise or maintainthe temperature therein so that the plastic to be released has theproper viscosity.

Such viscosity permits the ready disposition of the plastic material onthe upper face 34 of the sheet 30 as the sheet 30 is engaged by orgripped by the coating cylinder 50, and supported thereby during itsmovement under the trough 44. The rear wall 47 of trough 44 isstationary and provided with a lower tip opening 49 which is disposed adistance dt above the face 34 of the sheet 30. This distance correspondsto the thickness of the film as applied, and varies between 0.004 and0.0245 inches depending on the ultimate screen thickness desired. Thetip 49 may be regarded as an initial smoothing tip, because the coatingis subsequently ironed by the ironing cylinder.

As the sheet 30 passes under the trough 44, the same is movedcontinually by the coating cylinder 50 past the nib passageway 56. Inthis passageway, the coating, as applied to the face 34 of sheet 30, issmoothed so as to be regular and uniform throughout the entire areathereof. The spacing between the ironing cylinder and the coatingcylinder is equal to substantially the thickness of the ultimateproduct, or al temately, the distance between the ironing cylinder onthe face 34 of the sheet 30 is equal to dt. Thus, during the initialoperations of depositing a coating of predetermined thickness onto theforward face of the base sheet 30, and ironing such surface whereby itis uniform throughout its area, there is existent a coated base sheet.The coating is planar on both faces, i.e., the face adjacent andoverlying face 34 of sheet 30, and the forward face of the coating whichis spaced therefrom. During this stage of the process, the coating isstill sufficiently viscous to permit subsequent formation thereof, andat the same time, the viscosity thereof is sufficient to maintain thecoating sufficiently stable to permit passage of the coated unit to asubsequent operation immediately below. It will be understood that theseconditions are realized by having the proper melt temperature,viscosity, and set temperature relationships established. In otherwords, the plastic composition, aside from its optical characteristics,need have a melt temperature above ambient temperature, and a settingtemperature substantially no greater than ambient temperature, andpreferably slightly less than ambient temperature, and a viscositybetween such temperatures which permits the ready disposition thereof asa coating, and a smoothing thereof, as well as the formation thereof.

The semifinished unit comprising the base sheet 30, and the coating 60applied thereover, has been supported during previous operations withthe base sheet 30 adjacent the coating cylinder 50. However, as suchsemifinished unit is moved to a position within the nib passageway 80between the coating cylinder 50 and the embossing cylinder 70, it ispressed thereagainst in the nib passageway 80. Due to the viscosity andtackiness of the plastic, and the relative movement between the coatingcylinder 50 and the embossing cylinder 70. The semifinished unit istransferred from the coating cylinder to the embossing cylinder with thecoating 60 in engagement with the periphery of the embossing cylinder.

The embossing cylinder carries the groove 72 on the periphery thereof,and by virtue of the pressure exerted between the coating cylinder 50and the embossing cylinder 70, in the nib passageway 80, the coating 60is fonned into a plurality of ribsin the grooves 72 serving to shape thecoating into such form.

In order to achieve the desired end result the coating 60 has athickness prior to reaching the embossing cylinder of slightly less thanthe maximum thickness of the finished lenticular screen formed on thebase sheet 30. This differential in thickness is comparatively small, aswill be appreciated by reference to the ranges set forth above, but thisdifferential in thickness allows for compression of the plastic coatinginto the lens element shaped as described above. Specifically, clue tothe formation into the lenticular structure, while the coating becomesthicker, the volume is redistributed. Thus, the initial coating isapplied so as to have a volume corresponding substantially to theultimate volume of the lenticular screen after formation into lenticularelements by the embossing cylinder.

For purposes of carrying out the method described above in connectionwith FIG. 2, certain preferred apparatus embodiments hereof areincorporated in the assembly for selectively applying the coating to thebase layer 30. This phase of the invention is presented in FIGS. 3-5,inclusive. In FIG. 3, as in FIG. 2, the numeral 50 designates thecoating roller, the numeral 52 designates the ironing cylinder, and thenumeral 74 designates the embossing cylinder.

The trough 540 utilized for purposes of depositing a flowable viscousplastic in the manner prescribed in connection with FIG. 2, preferablyis constructed as shown in detail in FIG. 5. In this figure, the numeral47 designates the rear wall of the trough, and the numeral 46 designatesthe forward wall thereof. The wall 46, is fixed in relation to the wall47 whereby the base ends of the walls define therebetween the lower edgeof the trough, an opening 49 of predetermined width, preferably of theorder of 40 thousandths of an inch. In order to close the opening 49,the wall 46 is not movable as prescribed in connection with FIG. 2, andinstead, an auxiliary movable wall 500 is incorporated. The wall 500 hasa lower knife edge portion 502 which is adapted to move in abutting andcontacting relation with the lower end 504 (corresponding to edge 49,FIG. 2) of the rear wall 47 and in contacting relation to the lower edge506 of the fixed forward wall 46. Lower end 504 of wall 47 is disposedvertically below edge 506 of wall 47 thereby forming an inclined outletpassage.

The wall 500, as shown in FIG. 4, is slidable within inclined recessessuch as 510 formed in the end walls 512 and 514 of the trough framewhereby the wall 500 is mounted for reciprocal movement along aninclined axis extending parallel to the plane thereof, and the inclineof the outlet passage 49. In this manner, the wall 500 can be raised ormoved upwardly in the direction of the arrow 516, thereby moving thelower or tip end 502 clear of the base end 504 of wall 47 and allowingplastic carried within the trough 540 to move through the opening 49formed between the lower end of walls 46 and 47. As explained above,during this operation, when plastic is allowed to flow from the trough540, a base sheet 30 is being carried under the trough by the coatingroller 50 whereby a substantially uniform layer of plastic is depositedon the layer 30. When the layer 30 has moved to a position where thetrailing edge thereof is approaching the opening 49, then the wall 500is lowered to its original position in blocking relation to the opening49, thereby stopping the flow of plastic from the trough 540.

The plastic within the trough may possess properties whereby when thetrough is heated, the same is flowable under gravitational force ontothe face of the base layer 30. However, in certain instances, due to theproperties of the plastic, it may be desirable to force the same underpressure through the opening 49, and in this instance, pressure can beapplied within the inlet tube 252 of trough 540 to force plastic thereininto the trough and out through the opening 49 at the base thereof. Asconventional, and as suggested above, the depositing trough should beheated to maintain the plastic in a molten and sufficiently flowablestate for the depositing of the plastic in either manner describedabove.

It had been found that the provision of the movable auxiliary wall 500yields certain advantages. In particular, if the wall 46 is movable assuggested in connection with FIG. 2, then the force required to causemovement thereof is dependent upon the adhesive force exerted by theplastic within the trough thereon. The movable wall 500 is not subjectedto the total adhesive-type force of the plastic, but instead, is onlysubjected to the force thereof in a limited area adjacent the opening49.

Thus, with the auxiliary wall, less force is required for movementthereof and substantially simpler means can be incorporated forselectively causing the necessary adjustment in position of the wall.Moreover, with the arrangement of FIGS. 3-5, opening and closing of thetrough can be more closely controlled both from the time standpoint andthe material depositing standpoint, i.e., closing can be obtainedinstantaneously to prevent excess plastic deposit on a base layer.

Various types of systems can be utilized to automatically achieve theselective movement of the wall 500 with passage of base layers undertrough 540. Any such means, however, must operated in times sequencewith movement of the base layer 30 relative to the outlet of the trough540. This times relation can be obtained from movement of any one of therollers incorporated in the coating and embossing system, or from theparticular feed arrangement utilized to sequentially move the sheetsinto processing position on the coating roller 50. For purposes ofillustration, in FIG. 3, the shaft 530 of coating cylinder 50 is shownas carrying a sliding plate adjustable cam arrangement 532. Such camarrangement is conventional and includes a pair of juxtaposed plateshaving projecting cam portions 534 and 536. The plates are rotatablyslidable relative to one another about the shaft 530 whereby the lengthof the cam surface formed by the respective cam projectioris 534 and536, can be adjusted as desired.

For the purposes of understanding the operation of the system of FIG. 3,assume that the cam arrangement 532 is adjusted with the projections inthe relative positions shown in such Figure. Further, assume that anelectromechanical control arrangement is operatively associated with thecams to cause selective movement of the wall 500.

In the illustration of FIG. 3, the electromechanical control arrangementincludes a microswitch 538 electrically connected with a solenoid 541.The solenoid is disposed to operate a linkage 542 pivotal about a fixedpivot shaft 544. The right end of the linkage 542 is pivotally connectedto the movable wall 500 by means of a conventional pivot connection 545.The left end of the linkage 542, as shown, is in contacting engagementwith an operating plunger 546 of the solenoid 541.

The microswitch 538 merely serves as a switching means to connect thecoil of the solenoid 541 with a source of power through the line 550.Solenoid 544 is of conventional design having the plunger element 546downwardly extendable upon energization of the solenoid coil, whereby toexert a downward force on the left end of the linkage 542 as shown.Thus, when the microswitch 538 is operated by the cam assembly 532, thesolenoid 541 is energized and the linkage 542 is pivotedcounterclockwise about the pivot shaft 544. This results in raising themovable wall 500 and opening the passageway 49 through the base of thetrough means 540.

In order to provide for automatic return of the wall 500 to its initialclosing position, a spring means such as designated by the numeral 552,is fixed at one of its ends to the wall 500 and the other of its ends tothe fixed end wall of the trough adjacent thereto. Preferably, two suchsprings 552 are provided so as to bias the wall 500 downwardly atopposite ends thereof and eliminate binding of the wall in the recesses510 mounting the same for sliding movement. Return spring arrangementsof this general type are conventional and the details as to theconnection thereof between the end wall and the movable wall can be madein any suitable manner.

It will be noted from the above that the time of opening of the trough540 is controlled by the length of the cam surface formed by the camprojections 53$ and 536. Since this length can be adjusted by virtue ofthe tip of cam assembly incorporated, and since the cam assembly itselfcan be set in proper timed sequence with movement of the base sheets 30over the coating roller 50, the opening and closing of the trough 540can be controlled so as to start disposition of the plastic immediatelyinward of the leading edge of the base sheet 30 and so as to stop thedisposition of the plastic immediately inward of the trailing edgethereof or immediately after the trailing edge of the most rearwardimage section on the base sheet 30.

Bearing in mind the manner in which automatic timed sequential plasticdepositing can be achieved with the apparatus provided, there is but oneadditional consideration of particular importance, and this relates tocontrol of the coating thickness. By reference to FIG. 5, it will benoted that the movable wall 500 can be moved to positions where theopenings of the trough is as great as the width of the passageway 49, oronly as great as some portion thereof. In other words, the opening atthe base of the trough 540 can be controlled by selective movement ofthe wall 500. In turn, since the wall 500 is movable under the action ofthe linkage 542, limiting the degree of pivoting of the linkage aboutthe shaft 544, serves to control the extent of upward movement of thewall 500. Thus, preferably, a stop means such as generally designated bythe numeral 560 in FIG. 3 is incorporated. Such stop means incorporatesa fixed support 562 and an adjustable abutment screw 564 threadablyengaged within the support 562. The tip 566 of the screw 564 limitsdownward movement of the left end of the linkage 542 as shown, and thusmoving the screw to a position where the tip 566 is closer to thelinkage 542, as shown, serves to decrease the opening of the trough 40,whereas adjusting the screw where the tip 566 is moved further from theleft end of the linkage 542, permits wider opening of the trough 540.'It will be understood that while the abutment means 560 has been shownas cooperating with the left 15nd of the linkage, the same couldcooperate with an abutment carried by the wall 500, or with the rightend of the linkage 542 as shown. Moreover, an adjustment means on thesolenoid controlling the movement of the plunger therein would serve thesame purpose. The important point to understand is that some means isprovided for selectively adjusting the movement of the wall 500 so as toin turn permit adjustment of the degree of opening of the trough 540.

CONCLUSION After reading the foregoing detailed description of theillustrative and preferred embodiments of the instant invention, itshould be apparent that the objects of this specification have beensuccessfully achieved.

Accordingly, what is claimed is:

1. An apparatus for making a composite laminated flexible lenticularscreen and backing sheet, said apparatus comprising a heated coatingroll, actuatable means for metering a uniform layer of predeterminedthickness of a melted plastic in advance of said coating roll, apressure roll disposed in spaced parallel relationship to said coatingroll to form a first nip spaced a finite distance from the locationwhere said metering means deposits said uniform layer onto said coatingroll, a chilled forming roll disposed in spaced parallel relationship tosaid pressure roll to form a second nip spaced a finite distance fromsaid first nip, the surface of said forming roll providing an embossingsurface formed in accordance with the desired lenticular screen, andmeans responsive to movement of one of said rolls to actuate said meansfor metering, whereby when a backing sheet is fed through said firstnip, a coating of melted plastic of predetermined thickness is appliedto said backing sheet at said first nip, and when said backing sheet isthereafter fed with said plastic thereon through said second nip, alenticular configuration is embossed in the surface of said plastic,said chilled forming roll serving to sufficiently set base layer pastsaid outlet passage.

3. The combination defined in claim 2 wherein said trough comprises aframe including a pair of fixed wall members having base ends definingan inclined outlet passage between base ends thereof, and wherein saidmeans for opening and closing said passage comprises an auxiliary wallmember mounted in said frame and reciprocal along an inclined axis atleast substantially parallel to said passage.

1. An apparatus for making a composite laminated flexible lenticularscreen and backing sheet, said apparatus comprising a heated coatingroll, actuatable means for metering a uniform layer of predeterminedthickness of a melted plastic in advance of said coating roll, apressure roll disposed in spaced parallel relationship to said coatingroll to form a first nip spaced a finite distance from the locationwhere said metering means deposits said uniform layer onto said coatingroll, a chilled forming roll disposed in spaced parallel relationship tosaid pressure roll to form a second nip spaced a finite distance fromsaid first nip, the surface of said forming roll providing an embossingsurface formed in accordance with the desired lenticular screen, andmeans responsive to movement of one of said rolls to actuate said meansfor metering, whereby when a backing sheet is fed through said firstnip, a coating of melted plastic of predetermined thickness is appliedto said backing sheet at said first nip, and when said backing sheet isthereafter fed with said plastic thereon through said second nip, alenticular configuration is embossed in the surface of said plastic,said chilled forming roll serving to sufficiently set the embossedplastic to cause the same to maintain its lenticular configuration. 2.In combination with apparatus for selectively depositing a plasticcoating on a series of base layers, plastic-depositing means comprisinga trough having an elongate outlet passage therein and selectivelyoperable means for opening and closing said passage, roller means forconveying a base layer under said outlet passage, and means forselectively operating said means for opening and closing said passAge intimed relation to movement of said roller means and thereby movement ofa base layer past said outlet passage.
 3. The combination defined inclaim 2 wherein said trough comprises a frame including a pair of fixedwall members having base ends defining an inclined outlet passagebetween base ends thereof, and wherein said means for opening andclosing said passage comprises an auxiliary wall member mounted in saidframe and reciprocal along an inclined axis at least substantiallyparallel to said passage.